Polycarbonates are a versatile class of resins. It is desirable to improve the physical properties, and particularly the toughness and processability of the polycarbonates.
There are several patents which propose to improve the impact resistance of polycarbonate resins by incorporating therein a styrene-acrylonitrile type polymer. Representative of this art are U.S. Pat. Nos. 4,544,706 issued Oct. 1, 1985 and 4,564,654 issued Jan. 14, 1986. The compositions of the present invention do not incorporate acrylonitrile containing polymers.
U.S. Pat. Nos. 4,530,965 and 4,696,972 issued July 23, 1985, and Sept. 29, 1987 disclose the modification of polycarbonate resins with styrene-maleic anhydride type resins. The present invention does not contemplate the use of such resins.
U.S. Pat. No. 4,461,868 issued July 24, 1984 discloses a tertiary blend of polycarbonate resin with a thermoplastic alkyl acrylate and an acrylate grafted onto a rubbery core such as polybutadiene. The present invention does not comtemplate such a composition.
U.S. Pat. No. 4,680,337 issued July 14, 1987 discloses a method to make a thermoplastic polymer having good elongation and a high degree of clarity. The patent does not suggest the polymers could be used to modify the properties of polycarbonate resins.
The present invention seeks to provide novel polycarbonate graft copolymer blends having improved physical properties.